The present invention relates to a process for the preparation of reactive cyclodextrins, cyclodextrin derivatives or mixtures thereof, to a textile material dressed therewith, and to the use thereof.
Cyclodextrins are to be understood generally as being cycloamyloses and cycloglucans which are formed as cyclic dextrins by the action of cyclodextrin glycosyltransferase in the degradation of starch by Bacillus macerans and/or Bacillus circulans. They consist of 6, 7 or 8 glucose units α-1,4-linked to form a cyclic structure, thereby defining the α-, β- and γ-cyclodextrins, respectively, and are compounds of a kind which may be represented by formula I

The cyclodextrins have a ring size wherein n is 5, 6, 7 or 8. The substituent R is defined as an OH group.
Cyclodextrins are bound into a crystal lattice and are so layered on top of one another that they form continuous intramolecular channels in which hydrophobic guest molecules, e.g. gases, alcohols or hydrocarbons, may be included in varying amounts up to saturation. That process is referred to as “molecular encapsulation” (“molekulare Verkapselung”, Römpp “Chemie Lexikon”, Vol. 2, 1995, 9th expanded edition). By virtue of that property, cyclodextrins are used in the production of foods, cosmetics, pharmaceuticals and pesticides and also in solid-phase extraction.
A large number of reactive cyclodextrin derivatives and processes for their preparation are already known. EP-A-0 483 380 discloses a process in which the bonding of cyclodextrins (the abbreviation CD will be used in formulae herein below) to polymers by way of an acetal bond is described. In the preparation of those cyclodextrin derivatives, aldehyde groups in protected or unprotected form are introduced into the cyclodextrin compounds. These compounds then react with the nucleophilic hydroxyl groups of a polymer. The disadvantage of that bonding is the low stability of acetals in respect of acidic conditions.
It is also known for β-cyclodextrin to be reacted under aqueous conditions with epichlorohydrin under Lewis acid conditions. The article by A. Deratani and B. Pöpping in Makromol. Chem., Rapid Commun. 13, 237-41 (1992) describes that β-cyclodextrin can be reacted under aqueous conditions with epichlorohydrin under Lewis acid conditions using Zn(BF4)2 as catalyst to form a cyclodextrin-chlorohydrin (3-chloro-2-hydroxypropyl-cyclodextrin derivative). That derivative is capable of reacting under basic conditions with nucleophiles such as, for example, OH− ions. The disadvantage of that reaction is that, under the Lewis acid conditions, it is possible to achieve only a very low degree of incorporation of epichlorohydrin. For that reason, a large excess of epichlorohydrin is employed. However, those large amounts give rise to toxic or carcinogenic subsidiary products, which have to be separated off and destroyed.
DE-A-44 29 229 discloses the preparation and use of cyclodextrin derivatives containing at least one nitrogen-containing heterocycle having at least one electrophilic centre. The nitrogen-containing heterocycles are usually tirazines and quinoxalines which are used as reactive anchors for bonding to, for example, membranes, foils, films, textiles, leather, chromatographic separation phases etc. In the case of those materials dressed with β-cyclodextrin, the cavities in not all the fixed cyclodextrins are accessible.
Such reactive anchors are well known from textile dyeing. In the case of that process too, subsidiary products—so-called hydrolysates—are formed in the course of the bonding, which cannot be reused and consequently have to be disposed of as waste.
The problem of the present invention is consequently to make available a process which gives rise to only a small amount of harmful or non-reusable subsidiary products and which does not have the otherwise known disadvantages of the prior art, but which is at the same time suitable for the reaction with cellulosic and proteinic materials, especially fibres.